Comb copolymers for regulating cell-surface interactions

Abstract

Synthetic comb copolymers which elicit controlled cellular response, methods of applying these polymers to various surfaces, and methods of using the polymers for modifying biomaterial surfaces, in tissue engineering applications and as drug delivery devices are provided. The comb copolymers are comprised of hydrophobic polymer backbones and hydrophilic, non-cell binding side chains which can be end-capped with cell-signaling ligands that guide cellular response. By mixing non-cell binding combs with ligand-bearing combs, the surface concentration and spatial distribution of one or more types of ligands, including adhesion peptides and growth factors, can be tuned on a surface to achieve desired cellular response. In one embodiment, the combs are used as stabilizing agents for dispersion polymerization of latexes. The comb-stabilized latexes can be applied to substrates by standard coating operations to create a bioregulating surface, or used as drug delivery agents. In another embodiment, the combs can be blended in small quantities to a hydrophobic matrix polymer and processed to affect the surface segregation of the comb. The comb copolymers are formed in one embodiment by providing a biodegradable polyester backbone that includes reactive groups, and reacting the reactive groups in the backbone with reactive chain ends on a low molecular weight hydrophilic polymer. In another embodiment, non-biodegradable comb copolymers are formed by free radical synthesis of a hydrophobic monomer and a hydrophilic macromonomer. In all of the above embodiments, a portion of the hydrophilic polymer side chains can be covalently coupled to cell-signaling ligands such as adhesion peptides or growth factors to control cellular response.

We claim:  
     
       1. A method for engineering tissue comprising growing cells on a tissue-engineering matrix formed of or coated with the cell-regulating, comb-type copolymer comprising: 
       a) a hydrophobic polymer backbone;  
       b) non-cell binding hydrophilic polymeric side chains grafted to the polymer backbone, wherein the side chains have a molecular weight between 200 and 2000 Daltons;  
       wherein between zero and 100% of the non-cell binding, hydrophilic side chains are end-capped with cell-binding or cell-signaling ligands to form short cell-binding copolymer side chains and  
       wherein the side chains comprise less than 60% of the total copolymer weight,  
       wherein the comb copolymer is effective in regulating cellular adhesion or response to the surface.  
     
     
       2. A polymer latex comprising polymer particles dispersed in aqueous-containing media stabilized by cell-regulating, comb-type copolymer comprising: 
       a) a hydrophobic polymer backbone;  
       b) non-cell binding hydrophilic polymeric side chains grafted to the polymer backbone, wherein the side chains have a molecular weight between 200 and 2000 Daltons;  
       wherein between zero and 100% of the non-cell binding, hydrophilic side chains are end-capped with cell-binding or cell-signaling ligands to form short cell-binding copolymer side chains and  
       wherein the side chains comprise less than 60% of the total copolymer weight.  
     
     
       3. The polymer latex of claim  2  wherein the comb copolymers serve as a stabilizing agent during the latex synthesis. 
     
     
       4. The polymer latex of claim  2  whereby the comb copolymer comprises less than 1% of the latex dry weight. 
     
     
       5. The polymer latex of claim  2  further comprising non-cell-binding comb copolymers whose side chains are not end-capped with cell-binding or cell-signaling ligands. 
     
     
       6. The polymer latex of claim  2  further comprising latex particles stabilized by non-cell binding comb copolymers to achieve a defined mixture of non-cell binding and ligand-modified cell-regulating latex particles. 
     
     
       7. The polymer latex of claim  2  in which non-cell binding side chains of the comb copolymers at the surface of the particles are end-capped with ligands after the latex particles are synthesized. 
     
     
       8. Polymer coatings and films that regulate cell behavior prepared by casting a polymer latex comprising polymer particles dispersed in aqueous-containing media stabilized by cell-regulating, comb-type copolymers comprising: 
       a) a hydrophobic polymer backbone;  
       b) non-cell binding hydrophilic polymeric side chains grafted to the polymer backbone, wherein the side chains have a molecular weight between 200 and 2000 Daltons;  
       wherein between zero and 100% of the non-cell binding, hydrophilic side chains are end-capped with cell-binding or cell-signaling ligands to form short cell-binding copolymer side chains and  
       wherein the side chains comprise less than 60% of the total copolymer weight.  
     
     
       9. The polymer films and coatings of claim  8  prepared by casting a mixed latex of microparticles stabilized with the non-cell binding comb copolymers to achieve a defined mixture of non-cell binding and ligand-modified cell-regulating latex particles. 
     
     
       10. The polymer films and coatings of claim  8  comprising discrete domains of a single type of cell-signaling ligand against a background of non-cell binding hydrophilic side chains, where the domain size is on the order of the latex particles. 
     
     
       11. The polymer films and coatings of claim  10  wherein the domain size is between 0.1 and 10 microns in diameter. 
     
     
       12. The polymer films and coatings of claim  8  comprising discrete domains of multiple cell-signaling ligands against a background of non-cell binding hydrophilic side chains, wherein the domain size is on the order of the latex particles. 
     
     
       13. The polymer films and coatings of claim  12  where the domain size is between 0.1 and 10 microns in diameter. 
     
     
       14. The polymer film or coating of claim  8  in which non-cell binding side chains of the comb copolymers at the surface of the applied film or coating are end-capped with ligands after the coating or film is prepared. 
     
     
       15. A method of making polymer coatings and films that regulate cell behavior comprising casting a polymer latex comprising polymer particles dispersed in aqueous-containing media stabilized by cell-regulating, comb-type copolymers comprising: 
       a) a hydrophobic polymer backbone;  
       b) non-cell binding hydrophilic polymeric side chains grafted to the polymer backbone, wherein the side chains have a molecular weight between 200 and 2000 Daltons;  
       wherein between zero and 100% of the non-cell binding, hydrophilic side chains are end-capped with cell-binding or cell-signaling ligands to form short cell-binding copolymer side chains and  
       wherein the side chains comprise less than 60% of the total copolymer weight.  
     
     
       16. The method of making polymer film or coatings of claim  15  wherein non-cell binding side chains of the comb copolymers at the surface are end-capped with ligands after the coating or film is prepared.